Preservation of fibrous products



Patented Nov. 14, 1933 UNITED STATES PRESERVATION OF FIBROUS PRODUCTS Elbert C. Lathrop and Fergus A. Irvine, Chicago, Ill., assignors to The Celotex Company, Chicago, 111., a corporation of Delaware No Drawing. Application June 2'1, 1930 Serial No. 464,423

36 Claims.

This invention relates to a new and improved treatment, its method of application, and the product thereof, whereby wood, both as timbers and fiber, textiles and materials comprising fiber of vegetative origin, may be preserved and priotected from attacks of insects, fungi, and the The invention in its broad aspect, but more specifically, relates to the process of introducing into fibrous objects or depositing on fibers arsenic in a relatively insoluble form, and especially to the application of the process to the preservation of fibrous products manufactured by sheeting, felting, and the like" from fiber derived from vegetative sources and prepared for use by appropriate digestion and mechanical treatment whereby it has been separated into fiber bundles and individual fibers.

Further in its broad application the invention comprehends the use of a watersolution of arsenic, in any form, in which, while leaving the pulped material in suspension therein, a precipi- & tating or coagulation agent precipitates or throws out of the suspension onto the fiber a relatively insoluble simple or complex arsenical.

' It is well-known that aresnic in various forms is widely used in sprays and as dusting powders for protection against fungi, insects, etc., but that such uses are of limited application in that they comprise merely the surface application of relatively soluble forms of arsenic. As opposed to prior practice, this invention provides a means for, and has for its particular object, the intro duction integrally to materials, in mass, of a relatively insoluble form of arsenic. Not only does this invention disclose a simple method for treatment of materials with arsenic, but the method of application is extremely simple, and the cost, both of the treatment and of the chemicals, is

40 very low.

This method for the application of arsenic is probably based primarily on the phenomenon of adsorption, although the exact action of certain phases of the invention has not as yet been fully determined. The basis of the treatment is the probable adsorption of arsenious acid by hydrous metallic salts, particularly by hydrous ferric oxide, and the subsequent fixation of the ironarsenic complex on the fiber. Literature is divided with respect to the action of ferric hydrooxide in holding arsenious acid; some writers maintain this to be a pure adsorption phenomenon, while others contend that there is a chemical combination, but for the purpose of this invention the form of the action is immaterial.

In another phase of the invention, by the addition of a protective or anti-precipitant such as glucose, glycerin, and the like, a complex solution containing a ferric hydroxide-arsenious acid complex may be introduced into wood timbers and the like wherein, on drying, the ferric hydroxide-arsenious acid complex is integrally percipitated as a relatively insoluble precipitate which is available for the production of arsenious acid in toxic concentration.

Inpractice the preferred method of application, for the protection of that class of materials designated as insulation board or in fact for the protection of any article formed from a fiber pulp, is extremely simple, and the protection is integrally distributed throughout the material. The treatment is applied in the ordinary course of manufacture, preferably subsequent to the usual sizing treatment with rosin and alum, and involves only the addition of a solution of arsenious acid to a fluid suspension of the pulp, with the subsequent addition of the requisite amount of freshly formed ferric hydroxide prior to formation of the pulp into the finished article, or, if desirable, the chemicals may be added in inverse order or at the same time.

Whereas it has just been stated that a solution of arsenious acid is added to a fluid suspension of pulp, it is to be understood that the invention does not comprehend the addition of only arsenious acid as such. Most ordinary forms of arsenic, when in Water solution, decompose to form ortho-arsenious acid HsASOi; therefore, throughout this specification the term arsenious acid is used to designate a water solution of arsenic in which the arsenic trioxide A5203 radical in a water soluble compound is generally the active constituent for the purposes of this invention. The invention, though, is not to be understood to be limited only to the use of water soluble arsenic compounds, as relatively insoluble arsenic compounds may be incorporated by the use of suspensions thereof.

The chemical solution of arsenic or suspension mentioned just above is appropriately precipitated or coagulated and thrown down on or among the fibers and is distributed throughout the fluid pulp suspension from which the pulp is formed on screens while the water drains away, as is usual in the paper and fiber art. When forming the pulp, from the suspension, on

screens, the initial fiber deposited on the screens (ill) It is readily seen that in accordance with the procedure just described in order to incorporate a protective agent in a fiber board product it is only necessary to have a protective agent, which may be an arsenical or other insecticide or fungicide, as a precipitate or colloid, in suspension in a fluid suspension of pulp whereby as the normal procedure of formation of the final pulp mass on screens the preservative is filtered out by and retained in the pulp mass.

While in this specification there have been mentioned in various places complex colloid and precipitate, attention is directed to the fact that so far as the invention hereof is concerned, the words colloid and precipitate should be used in substantially an interchange able sense; that is, the chemistry of the reactions which occurs is not in all cases clear and it is very possibleand even probable-that certain actions which are referred to as precipitations actually involve colloid phenomena, whereas certain actions referred to as colloid phenomena probably involve pure precipitation, and further it is quite probable that many of the reactions involved comprise the combination of chemicalprecipitation and colloid phenomena.

In practice, to a fluid suspension of pulp at about 0.75% concentration there is added a solution of arsenious acid in an'amount equivalent to, say, 1% of A5203, based on the dry weight of the fiber. Conveniently, the requisite amount of ferric chloride in the ratio of Fe to As of approximately 111 is subsequently added with preferred adjustment of the pH to about pH 6 for the formation of hydrous ferric oxide, but such additions may be varied as stated in the preceding paragraph, and the iron salt may be added at some pH other than pH 6. If the iron salt is added at a pH other than pH 6, it must be subsequently adjusted to a suitable value to obtain precipitation which, dependent on the presence of electrolytes, etc., may be between about pH 4:.0 and pH 12.0. While the use of ferric chloride has been particularly mentioned, it is to be understood that other soluble ferric salts may be used in place thereof, or a ferrous salt may be used, but preferably one which will be oxidized when in solution.

It apparently is of considerable advantage to form the colloidal precipitate of the ferric hydroxide in place in the solution, since. in-this way the colloid is obtained in an absolutely fresh condition, in which state it seems much more active in adsorbing or combining with the arsenious acid than if prepared separately and subsequently added as the hydroxide.

The arsenious acid is adsorbed by the freshly formed ferric hydroxide, and this colloidal complex formed is in turn affixed to the fiber. The fiber is then passed to the necessary screens and the like, and the suspension fluid, the white water, is drained 01f, the fibrous mass then acting as a filter to retain the arsenious acid and iron salt complex. Analytical investigation of the white water from the treatment of fiber as just described has shown it to be either absolutely free or almost absolutely free of arsenic, whereby it is indicated that the affixation or retention has been complete. In practice economics may indicate a lesser adsorption of the arsenic as desirable, and this may be controlled by reduction of the ratio ferric hydroxide to arsenious acid, or, since the toxicity of the complex depends somewhat on the ratio Fezlis, it may be desirable to reduce this ratio to obtain greater toxicity.

For the treatment of materials in mass, such as for the treatment of timbers and the like, the procedure must be somewhat modified, although basically it. remains the same. The processes described above would not be satisfactory, due to the fact that all of the arsenious acid-ferric hydroxide complex would be afilxed to the surface fibers of the mass, and the interior thereof would be unprotected.

The difficulty just described is obviated by adding to the treating solution a protective agent such as glycerin, glucose, or the like, which will inhibit precipitation of the ferric hydroxide. The mass to be protected can be saturated to any desired extent with the solution just described and, on subsequent drying, the effectiveness of the antiprecipitant will be lost, and the protective arsenious acid-ferric hydroxide complex will be deposited as has been described.

A further method of applying this treatment to timbers and the like is to make a solution of, for instance, ferric chloride and arsenious acid at a pH lower than that for precipitation whereby the hydroxide is not formed. The timber would be saturated with this solution and subsequently soaked in a weak solution of alkali or alkali salts to form the ferric hydroxide-arsenious acid complex, which would form in situ within the timber.

While the use of ferric hydroxide has been particularly discussed as an element of the relatively insoluble toxic complex, it is to be understood that other hydroxides, for economic or other reasons, such as those of alumina and magnesia, may be substituted, although less satisfactorily, as the adsorption of the arsenious acid thereby is considerably less than the adsorption by the ferric hydroxide, and also that the arsenic may be in a form other than as arsenious acid.

It is obvious that those skilled in the art may vary thesteps and combinations of steps constituting the method, as well as vary the procedure of treatment, within the scope of this invention without departing from the spirit thereof, and for a fuller understanding of the various phases of the inventions hereof attention is directed to Patents 1,880,965 and 1,880,966 directed to various of the specific phases of the general inventions herein involved; the applications for which patents were co-pending with this case and in each of which one of the inventors-herein is a coinventor therein.

What is claimed is-- 1. A vegetative fiber mass having incorporated therein a colloidal complex comprising ferric hydroxide and arsenious acid.

2. Prepared fiber derived from vegetative growth and treated with ferric hydroxide and arsenious acid.

3. Vegetative fiber to which, while in dilute suspension, there has been added arsenious acid and freshly precipitated hydrous ferric oxide, the diluant subsequently removed and the fiber dried.

l. Vegetative fiber to which, while in dilute suspension, there has been added arsenious acid and freshly precipitated hydrous ferric oxide prepared in situ in the solution by the addition thereto of ferric chloride at a pl-Zi of approximately pH 6.

5. Fibrous material having applied thereto an insecticide and fungicide comprising a dispersion of a colloidal complex, an element of which correprises arsenious acid, a second element comprising freshly precipitated but peptized ferric droxide in combination with an anti-precipitant,

preventing final precipitation of the ferric hydroxide and wherein the colloidal complex is precipitated on the fibrous material by the antiprecipitant being rendered inactive.

6. A fibrous mass derived from vegetative sources having distributed therethrough an insecticide and fungicide comprising a precipitate formed, integrallytherein, from a solution containing arsenious acid and ferric salts, the final precipitation caused by initial precipitation of ferric hydroxide.

'7. A fibrous cellulose substance having ad'- sorbed therein a liquid comprising ferric hydroxide, arsenious acid, and an anti-precipitant, the fibrous cellulose substance being subsequently dried.

8. A product comprising fibers derived from vegetative sources having incorporated integrally therein an insecticide and fungicide comprising the precipitate formed in a solution containing arsenious acid and a metallic element capable of precipitation in the form of a gelatinous basic salt.

9. The method of protecting fibers derived from vegetative substances from attack by insects, fungi, and the like, comprising the incorporation therein of an insoluble colloidal complex including arsenious acid. a

10. The method of protecting fiber derived from vegetative substances from attack by insects, fungi, and the like, wherein arsenious acid as an element of a relatively insoluble colloidal complex is incorporated into the substances.

11. The method of protecting vegetative substances from attack by insects, fungi, and the like, comprising the addition, to a water suspension thereof, of arsenious acid and ferric chloride, adjustment of the reaction of the suspension to about pH 6 with subsequent removal of the water from the substances.

12. The method of providing protection for fibrous cellulose substances from the attack of insects and fungi, wherein the fibrous cellulose substance is impregnated With a solution containing an arsenical as an element of a colloidal complex, there being present in the impregnating solution a substance inhibiting precipitation therein, the fibrous cellulose substances after impregnation being dried, whereby the precipitation-inhibiting agent becomes inactive and the protective agent is deposited in situ.

13. The method of preserving products composed of fibers of vegetative origin by applying throughout the mass of the fibrous substance a relatively water insoluble toxic and inhibiting form of arsenic, and wherein in the presence of the fiber in dilute fluid suspension a precipitant is caused to react with an arsenical to precipitate the arsenical, thereby forming a precipitate in the fluid suspension, the precipitate in .the formation of the product being removed from the suspension fluid and concomitantly retained distributed throughout the fibrous product upon formation of a product therefrom formed by filtration of the suspending fluid through the fiber metal salt by deposition thereof on a foraminous member through which the suspending fluid is drained, the deposited fiber serving as a filter bed retaining the particles of the protective toxic metal salt.

15. The method of producing a product composed of felted fibrous materials, of vegetative origin, having integrally incorporated therein in the process ofmanufacture a water-insoluble toxic metal salt; wherein the product is formed from a fluid suspension of dispersed particles of the water-insoluble toxic metal salt and fiber by deposition of the fiber on a foraminous member through which the suspending fluid is drained, the felted fiber deposited serving as a filter bed to separate from the suspension fluid, and to retain, interspersed among the felted fibers the particles of the water insoluble toxic metal salt.

16. A product composed of felted fibrous materials of vegetative origin having integrally distributed therethrough amongst the fibers, in

' formation of a product therefrom.

18. A manufactured fiber product having distributed throughout the body thereof an insect and fungi inhibiting substance comprising the reaction product of a metalloid of the arsenic family and a precipitant.

19. Amanufactured fiber product having distributed throughout the body thereof an insect and fungi inhibiting substance comprising the reaction product of an arsenical and a precipitant.

20. A manufactured fiber product having distributed throughout the body thereof an insect and fungi inhibiting substance comprising the reaction product of an arsenical and a salt of a metallic element capable of precipitation in the form of a gelatinous basic salt.

21. A manufactured fiber product having distributed throughout the body thereof an insect and fungi inhibiting substance comprising the reaction product of a metalloid of the arsenic family and a salt of a metallic element capable of precipitation in the form of a gelatinous basic salt.

22. A manufactured fiber product having distributed throughout the body thereof an insect and fungi inhibiting substance comprising the reaction pfoduct of a metalloid of the arsenic family and alum.

23. A manufactured fiber product having distributed throughout the body thereof an insect and fungi inhibiting substance comprising the reaction product of an arsenical and alum.

24. A rot and termite proofed fiber board comprising interlaced fibers carrying in the interstices thereof a toxic agent in the form of distributed finely divided particles of a substantially water insoluble toxic metal salt.

25. A rot and termite proofed fiber board come prising interlaced fibers and carrying dispersed therethrough in the interstices thereof a toxic agent in the form of finely divided particles ofa substantially water insoluble toxic salt of arsenic.

26. Aformed fibrous product, composed of interlaced cellulose containing fibers, having thereinand distributed therethrough in the interstices-thereof, in-finely divided form, particles of water insoluble substance inhibitory of the life processes of organisms destructive tocellulose containing fibers.

27. The process of incorporating into fiber products, formed by felting from a dilute water suspension of fiber, particles of substance inhibitory of the life processes of organisms destructive to such products, wherein the particles of the inhibitory substance caused to be present in the water suspension of fiber are filtered out of the suspension and are integrally incorporated into the product in substantiallyuniform distribution in the interstices between the fibers thereof during and as the result of the operation of formation of the product from said fiuid suspension.

28. The process of producing felted cellulose containing fiber products having distributed therethrough in the interstices thereof and integrally incorporated therein, permanent protection against the action of the life processes of organisms destructive to cellulose wherein there is incorporated, in finely divided form, in a fiber containing pulp, prior to its formation into the product, a water insoluble protective agent inhibitory of and toxic to the life processes of said organisms whereupon, in the process of formation of the felted product, the protective agent is filtered from the liquid of the pulp by the fiber as it is felted and such protective agent is thereby retained inthe final felted fiber product integrally incorporated therein and distributed throughout the interstices thereof.

29. The method of making a fiber board or like article comprising precipitating a toxic metal salt in the presence of plant fiber.

30. The method of making a fiber board or like article comprising the incorporation therein mosa cs of a chemical compound containing a metalloid of the arsenic family, in the presence of plant fiber.

31. The method of making a fiber board or like article comprising precipitating a toxic metal: saltin the presence ofplant fiber with subsequent formation-of the fiber together with the precipitate into a formed product. W

32. A fiber product comprising a'shaped bodyof initially loose plant fiber having disseminated therethrougli crystals of a chemical compound inhibitory of-the life processes of organisms de-- structive to cellulosefiber. 33. Afiber product comprising a'shaped body of initiallylooseplant fiber having disseminated therethrough crystals of a chemical compound containing a metalloid of the arsenic family.

34. A fiber product comprising a shaped body of initially loose plant fiber having disseminated therethrough crystals of a chemical compound containing arsenic.

35. The method which comprises reacting, in the presence of plant fiber, upon'an aluminum salt in aqueous solution with arsenious acid, the reagents being proportioned to yield on the fiber a precipitate consisting substantially of an aluminum arsenate.

36. The method of protecting products composed of a shaped mass of initially loose fibers.

by depositing among the fibers throughout the mass thereof a relatively insoluble protective chemical compound inhibitory to the life processes of organisms from which said fibers are to be protected and wherein said protective chemical compound deposited throughout the mass is in the form of minute particles of such protective chemical formed and distributed throughout the fibers while in fiber suspension prior to formation of the product from such fiber suspension.

ELBERT c. LATHROP. FERGUS A. IRVINE;

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